Fightercat Cheetah Twin Build Question

[Finest Racing]

Hello, I am building a Fightercat Cheetah. I did a carbon fiber inlay this week and also did the chopped carbon fiber into the sponsons. The area I am stumped is the location of the rudder in relation to the props. I have attached a picture of the stinger resting against the boat and I am holding the rudder. From all the reading and pictures of Cheetah builds, I have seen the props between the boat and the rudder. Any suggestions? Anyone try this? I am building the boat to race in NAMBA P Offshore. Thank you
Would the rudder have any effect in the performance of the props or the performance of the boat since it is only an inch away from the boat?

Cheetah Rudder & Stinger.jpg Cheetah rudder.jpg Cheetah Inlay.jpg

[Finest Racing]

Installed the stingers todays and smeared some epoxy across the rear panel with carbon fiber chips.
Tomorrow I am installing the rudder and expandable foam in the front.
Sunday I hope to epoxy the motor mounts in place.

Cheetah Rear Inlay.jpgCheetah Stinger Rear View 02.jpg

[TheShaddix]

Solid progress! To answer your question, the rudder will have no affect on the props, especially at speed. For the rear section I would suggest just flooding it with epoxy and cf bits instead of smearing it over the surface.
Also, when you do the expandable foam, fill your bathtub full of cold water and when the foam is expanding dip the bow into the water to avoid deformation due to heat. Pour foam in 2-3 stages, this way it will look much better. If you mix your second batch too small, it will just sip into the side cracks of the first foam batch and look quite uneven. So it's best to just pour fewer but larger batches and not try to go up to the very top. If you end up pouring too much, do not try to scoop it out! Just let it cure, then cut out the excess.

[Finest Racing]

Thank you for the tips. I did mix the cf in with the epoxy as I was mixing it. Amazing how it cured so quickly when I mixed the cf in it as I was mixing it. I was still able to spread it across the rear evenly.
The bath tub is a neat trick. Thanks.
I figured I would need to do the foam a few times to get the correct amount and to also make it look good.
Thanks again, great advise.

[ls1fst98]

I'd prefer to not use expanding foam and instead use that pink foam sheet insulation cut to fit. So in case you ever needed to make a repair it's easy to remove and gain access

[Finest Racing]

I'd prefer to not use expanding foam and instead use that pink foam sheet insulation cut to fit. So in case you ever needed to make a repair it's easy to remove and gain access

Good point. It would be a challenge to make a repair with the foam. I have been using pool noodles and thought I would try the foam. Thanks for the thought.

[Fella1340]

+1 on not using expanding foam. I dropped my unfinished genesis on the sponson tip and created a small hole. Easy to fix properly and disturbed very little of the painted outside surface. Had it been foamed in it would have been a messy patch job that couldn't be repaired properly. Lots of guys love the foam though. Still mixed reviews of how it stands up over time, many mentions of hull sucking down after a couple years etc.

[Finest Racing]

+1 on not using expanding foam. I dropped my unfinished genesis on the sponson tip and created a small hole. Easy to fix properly and disturbed very little of the painted outside surface. Had it been foamed in it would have been a messy patch job that couldn't be repaired properly. Lots of guys love the foam though. Still mixed reviews of how it stands up over time, many mentions of hull sucking down after a couple years etc.

Thanks, Did not hear about the long term results. I was thinking that the foam would help with strength on a fast boat bouncing on the water. I know that is one idea, with many negative thoughts.

[rickwess]

Once cured, 2 part polyurethane foam is stable. Full size boats use it for mandated floatation requirements. Perhaps if you take it on a plane the drastic change in pressure could affect the air bubbles.

Some people don't distinguish between spray foam and 2 part foam. Run away from spray foam.

[keithbradley]

Once cured, 2 part polyurethane foam is stable. Full size boats use it for mandated floatation requirements. Perhaps if you take it on a plane the drastic change in pressure could affect the air bubbles.

Some people don't distinguish between spray foam and 2 part foam. Run away from spray foam.

Are you 100% sure that there's no way it could shrink or grow over time? Keep in mind that telling someone it's stable could cost them a significant amount of money if you're wrong.

[Fluid]

Several of us have found out the hard way that at least some popular two-part foams are not 100 percent stable. I know that one boat in which I poured foam sold by a popular FE on-line store almost had the deck collapse after sitting in the sun on several days. The foam shrunk and sucked the deck down. Fortunately I was able to slip a hacksaw blade between the foam and deck and cut them apart. The deck eventually rose back to it's original shape - almost. Now when I use foam I use a release agent on the underside of the deck. I can't always keep my boats out of the sun.

[rickwess]

I've talked to the manufacturer, distributor (Composites Canada) as well as the builder of my custom ski boat who has used it for over a decade to meet Coast Guard regulations. I've done as much due diligence as possible before I let the bow of my ski boat to be foamed.

I obviously can't speak to all 2 part foams, but I did the research on this:

http://www.compositescanada.com/product-catalog/resins/product/305-pour-in-place-polyurethane-foam

[Finest Racing]

I did not say in my post that I was using a two part mix. The only time my boats see the sun are when they are running. I would think that would be a few hours a day and when racing maybe 5 to 6 hours. This past season I had a towel over my boat. I noticed that it was cooler then ambient temp.

[kfxguy]

I much rather two part foam. If you.crash and break the hull apart bad enough, your pool noodles or pink foam is all your gonna see floating...so what's the point? Two part foam is going to strengthen the hull and it also sticks to it. Break apart, good chance you'll still be able to get some stuff back besides pool noodles. To each their own tho....

[Finest Racing]

I much rather two part foam. If you.crash and break the hull apart bad enough, your pool noodles or pink foam is all your gonna see floating...so what's the point? Two part foam is going to strengthen the hull and it also sticks to it. Break apart, good chance you'll still be able to get some stuff back besides pool noodles. To each their own tho....

This was my first thought for using the two part foam. I see there are pros and cons to both. I think I will try the two part foam. Fingers crossed. I will post updates and pictures. Thanks everyone.